In composite antenna devices, such as a diversity antenna including plural antennas disclosed in Japanese Patent Laid-Open Publication No.2003-298340, isolation between the antennas generally needs to be large. A space between the antennas is set to be large as to increase the isolation between the antennas.
Mobile communication apparatuses, such as a mobile telephone, have been desired to have small sizes. A composite antenna device used in the communication apparatuses hardly has a large space between antennas of the composite antenna device, accordingly having a small isolation between the antennas.